Variable light dimming adaptors for incandescent bulbs



Nov. 24, 1970 B. c. GARRETT VARIABLE LIGHT DIMMING ADAPTORS FOR INCANDESCENT BULBS Filed May 7, 1968 INVENTOR BENNETT C. GARRETT FIG.5

J ms ATTORNEY United States Patent C US. Cl. 315-272 3 Claims ABSTRACT OF THE DISCLOSURE A light dimming adaptor for adapting a lamp fixture to variably illuminate an incandescent bulb from a dimoif condition to a full illumination condition. A body structure for the adaptor having a base portion and a socket portion houses the elements of a dimming circuit including a load semiconductor device and a potentiometer. The semiconductor device is positioned in the base portion in contact with a conductive screw sleeve provided on the outer surface thereof for dissipating heat generated by the semiconductor device, and the potentiometer is positioned in a cavity provided in the socket portion with a knob on the wall thereof for adjusting its setting to thereby control the intensity of illumination of the bulb.

This invention relates to light dimming adaptors for incandescent bulbs and more particularly to such an adaptor which houses an electronic circuit that enables the illumination of a bulb to be selectively varied from a full-off condition to a full-on condition.

It is highly desirable on many occasions to vary the illumination of floor or table lamps by switch controls provided on the lamp. This is usually provided for in residential environments by the use of three-way lamps. These lamps are constructed to utilize a type of incandescent bulb having two filaments. The switching mechanism of the lamp fixture selects either one or both of the filaments to be energied to thus provide three different illumination levels. In order to avoid the necessity of utilizing twofilament incandescent bulbs which are more expensive and have a tendency to burn out more quickly than single-filament bulbs, adaptors have been provided in the prior art which make it possible for a conventional lamp socket to accommodate a single-filament bulb to provide dual levels of illumination. The adaptor makes this possible by including within the structure thereof a diode rectifier connected to one of the terminals of the light bulb. A switch means included in the adaptor is used to open or close a circuit path bypassing the diode rectifier for thus establishing the dual levels of illumination in the light bulb mounted in the adaptor.

The present invention provides an improved adaptor over the prior art in that it includes within the body structure thereof an electronic circuit which provides for variably controlling the illumination of a lamp as de sired, from a dim-off condition to a full brilliance condition. Although the use of such variable, full range, control in light dimming circuits is known in the prior art for residential lighting systems, their use heretofore has been limited to wall-type installations. Examples of typical light dimming circuits useful for incorporation in the adaptor of the present invention are disclosed in US. Pat. No. 3,188,490. Such circuits utilize a multilayer semiconductor device which exhibits a thyratron type switching action for controlling the power supplied to the bulb. A firing circuit including a resistance-capacitance phase shift network is provided in the dimming circuit to produce a firing signal of different phase angle than the voltage applied to the bulb. The firing signal controls the point in each alternating current half cycle at which the load semi- Patented Nov. 24, 1970 conductor device becomes conductive and passes current to the bulb placed in series therewith. The firing circuit is manually adjusted by a potentiometer. In this manner the circuit controls the application of full wave power to the incandescent bulb and thus controls the intensity of illumination of the bulb.

It is thus seen from the above that when it is desired to provide an adaptor which will produce a full range of illumination in a light bulb, the adaptor must house a dimming control circuit comprised of several electronic components. These components must be physically fitted within the structure of the adaptor in a compact manner so as to provide a unit which is sufiiciently small in size so that when screwed into a lamp fixture socket it will not interfere with the mounting of an ordinary light bulb in the lamp. Furthermore, in such control circuits, the semiconductor device dissipates a certain amount of heat during its operation, and in order for the electronic dimming circuit to operate properly, the adaptor must house the semiconductor device to enable the transfer of heat from the enclosure of the adaptor to the environment without an excessive temperature buildup in the adaptor. The existence of a high temperature source in an adaptor for a lamp fixture is not only inherently unsafe but additionally the load semiconductor device will only operate reliably within a relatively narrow temperature range and will fail to operate at all if the temperature rises beyond a critical value.

These and other objects and features of the invention are achieved through the physical structure and arrangement of an electronic light dimming circuit which will allow it to be assembled in a novel compact manner within the body structure of the adaptor. More particularly, the load semiconductor device required in such a dimmer circuit is disposed within the adaptor so as to have thermal contact with a conductive screw sleeve provided on the base of the adaptor, thus utilizing the appreciable surface area of the sleeve as a heat radiating surface for controlling the transfer of heat from the semiconductor device.

The specific nature of the invention as well as other objects, advantages and features thereof will become apparent from the following description of the preferred embodiment in conjunction with the following drawings in which:

FIG. 1 shows the adaptor of the present invention positioned on a lamp fixture;

FIG. 2 is a perspective view of the two separate halves of the adaptor, together with the electronic assembly unit mounted therein;

FIG. 3 is a sectional view of the assembled adaptor taken along the lines 33 of the halves of the body structure shown in FIG. 2;

FIG. 4 is a perspective view of the electronic assembly unit including the components of the dimming circuit;

FIG. 5 is a schematic diagram of a typical dimming circuit for incorporation in the adaptor of the present invention; and

FIG. 6 shows the two halves of the body structure mated together to form the assembled adaptor.

Reference will first be made to FIG. 1 showing a conventional lamp fixture 10 provided with adaptor 12 which is constructed in accordance with the teachings of the present invention. It should be noted that the adaptor 12 is relatively small in size and does not extend very high above the conventional socket 13 of the lamp fixture 10 so that an incandescent bulb 14 mounted in the adaptor 12 does not hit the lamp shade stirrup 15 or shade holder. The lamp fixture socket 13 is provided with a conventional on-off rotary switch 17. The adaptor is provided with a knob 18 which can be turned to provide a variable illumination of the bulb 14 from dim-off to full brilliance. As will be made clear in the ensuing description, simply by turning the on-olf switch 17 the light bulb 14 may be turned on. Then by turning the knob 18, the light bulb may be controlled to any desired degree of illumination.

Referring to FIG. 2, a perspective view is shown of the two halves 12a and 12b forming the main body structure of the adaptor 12. The two halves are separated in order to show the associated electronic assembly unit 19 mounted therein. The halves of the body structure are preferably molded of a plastic insulation material such as polycarbonate. When the two halves of the body structure are mated, the lower smaller diameter end thereof forms a base portion 20 over which is fitted a one-piece conducting sleeve 22 having standard threads on the outer surface thereof. The base portion 20 is adapted to be screwed into conventional on-ofi type lamp fixture socket 13 to make electrical contact with the terminals thereof. The upper larger diameter end of the body structure forms a female socket portion 23 having internal standard threads for receiving the base of a conventional singlefilament on-off type light bulb 14 and making electrical contact with the light bulb terminals. The socket portion 23 of the body structure is separated from the base portion 20 by a divider 25 formed at the time the body structure is molded.

Reference is next made to FIG. which schematically illustrates a typical light dimming circuit which is incorporated in the adaptor 12 of the present invention. As disclosed in the previously referred to patent, the semiconductor device 26 controls the flow of current through the bulb 14. The capacitor 24, potentiometer 29 and resistors 33 and 34 of the circuit comprise the phase shift network utilized to produce a firing signal of different phase angle than the voltage applied across the bulb 14. The output of the phase shift network is applied across a controller semiconductor device 27 connected in parallel with a series circuit comprising capacitor 21 and the primary winding of transformer 28. When the controller semiconductor device 27 conducts in response to the firing signal it produces a large voltage pulse on the secondary of the transformer 28 causing the load semiconductor device 26 in series therewith to conduct current to the bulb 14. The phase angle of the firing circuit is adjusted by manipulating the potentiometer 29 to thereby provide for varying the load current to the bulb and thereby its intensity of illumination.

Referring back to FIG. 2, the hollow base portion 20 of the body structure has positioned therein a rectangular circuit card 30 on which are mounted the electronic components such as the capacitors 21 and 24, resistors 33 and 34 and semiconductor device 27 required for a typical power regulating circuit as exemplified by the circuit shown in FIG. 5. The load semiconductor device 26 is positioned on the card 30 such that wher the card is fitted into the hollow base portion 20 of the body structure, the end 26a of the casing of the load semiconductor device 26 fits into an opening 31 provided on the side of the base portion 20. Along the upper portion of the card 30 the transformer 28 is secured such that it is enclosed by the expandirg diameter portion of the body structure. Extending upwardly at an angle from the side of the card 30 and positioned in a passageway 44 formed between the base portion 22 and the socket portion 23 are a pair of stiff terminal members 32 which connect to the second circuit card 35 whose plane generally extends rormal to the plane of the first circuit card 30. The second card 35 fits into a cavity 36 provided on the side wall of the body structure surrounding the socket portion 23. The potentiometer is mounted on the outer surface of the second card 35 so as to be enclosed within the cavity 36. A strip terminal 38 is disposed on the inner surface of the second card 35 to fit in a vertical slot 39 provided in the threaded wall of the female socket portion 23 so as to make electrical contact with the threaded portion of the base of light bulb 14 which may be screwed into the socket portion 23. This strip terminal 38 is electrically connected by wire 40 to the potentiometer 29 and by a wire 41 to the transformer 28 located on the first circuit card 30.

Above the divider 25 forming the bottom of the socket portion 23 of the body structure is a spring terminal 43 which extends to a central position within the female socket portion 23 for the purpose of maintaining electrical contact with the central base terminal of the conventional single-filament light bulb 14. The other end of the spring terminal 43 is shaped to conform to the inside contour of the body structure as shown in FIG. 3, and extends down through the hollow base portion 20 of the body structure to central base terminal 45.

It should now be clearly understood from the above that the inner spring terminal 43 of the socket portion 23 is electrically connected directly to the central base terminal 45 of the base portion 20 of the body structure; and the outer strip terminal 38 of the socket portion 23 is electrically connected to the electronic circuit comprised of the components on the circuit board 30 and through the load semiconductor device 26 to the outer conductive sleeve 22 which corresponds to the outer terminal on the base portion 20 of the body structure. It should be noted that the components and terminals of the dimming circuit shown in FIGS. 2 and 3 are schematically indicated in the diagram of the circuit illustrated in FIG. 5 and designated by corresponding reference numerals.

As shown in FIG. 4, all the electronic components for the dimmer circuit including the potentiometer 29 are assembled to form an integral unit prior to being inserted in the body structure. The cards 30 and 35 are held in position relative to each other by the interconnecting stiff terminal members 32. The assembly is such that the respective cards with the components secured thereon as previously described can be readily inserted into the opening provided by the hollow base portion 20 and the opening provided by the cavity 36 formed in the wall of the socket portion 23 of one of the halves of the body structure. When the two halves of the body structure are aligned and mated, the tongue 47 located on the divider 25 on one of the halves is fitted into a groove 48 provided on the divider 25 of the other one of the halves. When so assembled, the potentiometer 29 is properly positioned in the cavity 36 with its shaft 37 extendthrough an opening 42 on the outer wall of the socket portion 23 of the body structure, and the end 26a of the casing of the semiconductor device 26 is positioned in the opening 31 provided on the outer wall of the base portion 20 of the body structure. The conductive sleeve 22 is fitted over the base portion 20 and a solder junction is formed so as to make electrical and thermal contact with the end 26a of the casing of the load semiconductor positioned in the opening 31. In addition to being held by the conductive sleeve 22, the two halves of the body structure are provided with a groove 49 on the upper end of the socket portion which groove is formed to provide a seat for a split circular spring 51 which holds the halves together.

It should now clearly be understood that the present invention provides a small adaptor 12, which is simple in its construction, and relatively inexpensive, for use in a lamp fixture 10 to adapt a lamp to variably control the illumination of a conventional single-element light bulb 14 inserted into the socket portion 23 of the adaptor. The adaptor 12 can be used without requiring any rewiring or the use of any other than conventional lamp fixtures and light bulbs. The conductive screw sleeve 22 and the load semiconductor device 26 which is in series with the lamp load and which conducts the load current are in direct thermal and electrical contact with each other. In a typical dimming control circuit for use in the present invention, the multilayer semiconductor device 26 has a maximum junction temperature rating of approximately 100 degrees centigrade and the power dissipated in the load semiconductor device is approximately 1.5 watts when the load is at 1.25 amps. Under such operating conditions, the maximum junction temperature would be quickly exceeded, destroying the semiconductor device if the heat generated by the device were not dissipated in the appreciable surface area of the conductive sleeve 22 and in the ambient air surrounding the female sleeve of the lamp socket and other parts in the socket of the lamp fixture 10.

It should be further noted that the socket portion 23 including the internal threads thereof is formed of a plastic insulating material. The only conductive surface is the strip terminal 38 recessed in the internal threads thereof. This arrangement aids in isolating the semiconductor device 26 from the heat generated in the light bulb 14. Furthermore the potentiometer 29 is completely enclosed within the cavity 36 provided in the side wall of the socket portion 23, thus assuring that no metallic surface of the adaptor is normally contacted during insertion of the adaptor 12 into a lamp fixture 10. Furthermore, using the conductive sleeve 22 located on the lower base portion of the adaptor for a heat dissipating structure avoids exposing to operator touch any conductive surface which is electrically alive. It is only when the base portion 20 is screwed into the lamp fixture socket 13 and the corresponding terminals of these members make contact, that the electronic circuit incorporated in the adaptor becomes energized such as to heat up the semiconductor device 26 and the conductive sleeve From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before described as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

It is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise the preferred form of several modes of putting the invention into effect.

What is claimed is:

1. A lamp fixture adaptor for providing variable illumination for a light bulb, comprising: a body structure having a hollow base portion and a socket portion, said base portion having a first and second terminal for making contact with corresponding terminals in an on-ofi socket of the lamp fixture, said second terminal on said base portion being in the form of a conductive screw sleeve substantially covering the base portion, and said socket portion having a first and second terminal for making contact with corresponding terminals of the light bulb, means for electrically connecting the first terminals of the socket and base portions of the body structure, a dimming circuit enclosed within said body structure including a load semiconductor device and a potentiometer, said circuit connected across the second terminals of the socket and base portions of the body structure with said semiconductor device enclosed within said hollow base portion and extending through an opening in the side wall thereof to contact said screw sleeve second terminal for providing an electrical and thermal conductivity path between said semiconductor device and said screw sleeve whereby heat produced in said load semiconductor device is dissipated in said screw sleeve making contact with a corresponding terminal in the on-off socket of the lamp fixture, and external means on said body structure for manually adjusting the setting of said potentiometer to control the application of power to the light bulb and thereby control the intensity of illumination of the bulb.

2. An adaptor for lamp fixtures comprising: a body structure formed of insulating material, said body structure having a hollow base portion for engagement in mating relation with a conventional on-oif type light socket and having an inner terminal and a screw sleeve outer terminal arranged to make contact with corresponding terminals of the light socket, said body structure having a socket portion provided with internal threads for engagement in mating relattion with a base of an incandescent light bulb and having an inner terminal and a strip outer terminal arranged to make contact with corresponding terminals of the light bulb, said socket portion provided with a cavity on the side wall thereof, means for electrically connecting the inner terminals of the socket and base portions of the body structure, a dimming circuit within said body structure including a potentiometer and a load semiconductor device, said circuit connected across the strip outer terminal of the socket portion and the screw sleeve outer terminal of the base portion with said potentiometer disposed in the cavity provided in the side wall of said socket portion and connected to said strip outer terminal and with said load semiconductor device extending through an opening in the side wall of the base portion to contact said screw sleeve outer terminal for providing an electrical and high thermal conductivity path between said load semiconductor device and said screw sleeve outer terminal, and external means on the socket portion of said body structure for manually adjusting the setting of said potentiometer to control the application of power to the light bulb and thereby control the intensity of illumination of the bulb.

3. The combination as claimed in claim 2 wherein said body structure is formed in two separate halves mated along the vertical central plane of the body structure,

wherein the interior of the body structure is formed with the hollow base portion having a passageway connecting to the cavity provided in the side wall of said socket portion for enclosing said dimming circuit, wherein the elements of said dimming circuit form a separate assembly comprising a first circuit card on which said load semiconductor device is mounted, a second circuit card on which said potentiometer and said strip outer terminal is mounted, and electrical interconnecting means for rigidly holding said cards in position relative to each other, and wherein said separate assembly is insertable between the respective halves of the body structure such that the first card is positioned in the hollow base portion with the semiconductor device thereon contacting the screw sleeve outer terminal through the opening provided in the side wall of said hollow base portion, and such that the second card is positioned in the cavity provided in the socket portion with the strip outer terminal thereon positioned in a slot formed in the internal threads thereof and with the potentiometer thereon accessible from the outside of the body structure.

References Cited UNITED STATES PATENTS 3,188,490 6/1965 Hoff et al. 32322 3,300,711 1/1967 Duncan 323-22 3,331,013 7/1967 Cunningham 323-22 3,355,612 11/1967 Peek 32322 3,452,215 6/ 1969 Alessio 315-208 X J D MILLER, Primary Examiner A. D. PELLINEN, Assistant Examiner US. Cl. X.R. 315200;32319, 22, 36,339-154 

